Mailinglist Archive: opensuse-buildservice (46 mails)

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[opensuse-buildservice] build stalls due to KVM running out of entropy
  • From: Hans-Peter Jansen <hpj@xxxxxxxxx>
  • Date: Tue, 26 Feb 2019 12:58:54 +0100
  • Message-id: <47011252.3lvlUn8XQ7@xrated>

I found a couple of certain packages suffering from build stalls until the
build is aborted. When retrying the build many times, it eventually succeeds
(most probably due to building on a build host, that doesn't suffer from this
issue for some reason).

While occasionally observable with all (x86) targets, it is reproducible with
a probability near 100 with old distributions like 13.2 (yeah, lame, I know..).

Given, that BS attempts to be target agnostic, let's take this as a chance to
determine and avoid this pitfall in the future for all kinds of targets.

Often, these stalls happen after a python3 sphinx-build is executed. Another
regular pattern for these stalls is during py.test3 runs.

I was able to track this issue down with "osc build --vm-type=kvm" for a 13.2
build and running build-sphinx with strace:

[ 11s] + cat /proc/sys/kernel/random/entropy_avail
[ 11s] 0
[ 11s] +
[ 11s] + strace -fttvs4096 -o.trc python3 build_sphinx
[ 11s] running build_sphinx
[ 11s] creating /home/abuild/rpmbuild/BUILD/pyOpenSSL-18.0.0/build/sphinx
[ 11s] creating
[ 11s] creating /home/abuild/rpmbuild/BUILD/pyOpenSSL-18.0.0/build/sphinx/html
[ 11s] Running Sphinx v1.7.6

where the trace log ends with:

1125 20:07:26.812659 open("/dev/random", O_RDONLY) = 4
1125 20:07:26.812741 fcntl(4, F_GETFD) = 0
1125 20:07:26.812765 fcntl(4, F_SETFD, FD_CLOEXEC) = 0
1125 20:07:26.812783 poll([{fd=4, events=POLLIN}], 1, 4294967295

As far as I can tell, the /dev/random reads are initiated from python3 (v3.7.2).
No idea, why it isn't using /dev/urandom, though.

Since KVM IS started with some rng mechanics in place:

/usr/bin/qemu-kvm -nodefaults -no-reboot -nographic -vga none -cpu host \
-object rng-random,filename=/dev/random,id=rng0 -device
virtio-rng-pci,rng=rng0 [...]

I wonder, why it doesn't appear inside the build:

/proc/sys/kernel/random/entropy_avail is 0 here.

In an attempt to fix this issue, I added this to the prjconf:

Preinstall: haveged
Runscripts: haveged

but that doesn't change the picture.

So the question boils down to:

How do I get (enough) entropy into the building KVM locally and in the BS?


Local system uses Linux 4.20.12, qemu-kvm-3.1.0, osc-0.164.2, build-20190123,
python 3.7.2
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